This invention relates to new propylene/ethylene/xcex1-olefin terpolymers. More particularly, the invention relates to propylene/ethylene/xcex1-olefin terpolymers having a relatively high molecular weight and a narrow molecular weight distribution and a specific elution characteristic in ortho-dichlorobenzene, which are produced using an olefin polymerization catalyst comprising a metallocene compound as a principal component.
A resin composition based on the terpolymer is suitable for the production of the molded products with improved blocking, heat-seal and hot tack properties, transparency and gloss.
The resin compositions based on olefin copolymers comprising propylene and ethylene as a principal component have been extensively used in the field of various moldings, because of their good mechanical properties, good chemical resistance and very useful balance with economy. These olefin copolymers have been produced by copolymerizing olefins in the presence of a catalyst comprising an inorganic transition metal catalyst component such as titanium trichloride, titanium tetrachloride and the mixtures thereof which are supported on a support such as magnesium chloride, in combination with an organoaluminum compound, what is called Ziegler-Natta catalyst system.
For instance, Japanese Patent Kokai 56-143207 discloses a propylene/ethylene/xcex1-olefin terpolymer comprising 88 to 96 mol % of a propylene unit, 1.5 to 5.3 mol % of an ethylene unit and 0.7 to 7.6 mol % of an xcex1-olefin unit of C4-C20, which is produced using Ziegler-Natta catalyst system. The molded products formed from the resin composition comprising the terpolymer as a base resin are excellent in rigidity and heat resistance.
In recent years, the processes for the production of olefin copolymers have been proposed wherein olefins are copolymerized using a metallocene catalyst system comprising an organic complex of a transition metal, so-called metallocene compound in combinatin with an aluminoxane which is different from prior Ziegler-Natta catalyst system. The olefin copolymers produced using the metallocene catalyst system are more homogenous than those using prior Ziegler-Natta catalyst system, since the molecular weight distribution (Mw/Mn) is narrow and comonomers are copolymerized homogeneously. In the homopolymerization of propylene, choice of metallocene species can produce a polymer which is high in stereoregularity of a propylene unit, i.e., isotactic index.
Journal of Molecular Catalysis A: Chemical 102 (1995) 59-65 mentions, with regard to the relationship between the polymerization temperature and the melting point of the resulting polypropylene using the metallocene catalyst system to provide isotactic polypropylene, that polypropylene of higher melting point is produced at 0xc2x0 C., but the melting point of polypropylene produced at an industrial polymerization temperature, e.g., 70xc2x0 C. becomes extremely low.
Organometallics 1994, 13, 954-963 describes that polypropylene of high melting point is produced even at 70xc2x0 C., an industrial polymerization temperature by selecting a metallocene compound in a homogeneous polymerization system using a catalyst component such as the metallocene compound not supported on a support.
In the polymerization process and apparatus which have been used in the manufacture of propylene copolymers, a supported catalyst having a catalyst component such as metallocene compound supported on a support has been required to use for industrially producing propylene copolymers using the metallocene catalyst system in place of Ziegler-Natta catalyst system.
WO94/28034 discloses that the melting point of polypropylene produced by polymerization of propylene using the supported catalyst having on the support the metallocene compounds providing polypropylene melting at high temperatures is lower than that of polypropylene produced by a homogeneous polymerization.
JPA-2-173016 discloses a heat-sealing agent comprising a propylene polymer wherein a propylene component is 90-100 mol %, an ethylene component is 0-10 mol %, an alpha-olefin component of 4-20 carbons is 0-10 mol %, a melting point (Tm) is in the range of 70 less than Tm less than 155-5.5 (100-P) in which p is the propylene content (mol %) present in the polymer, an intrinsic viscosity (xcex7) as measured in decalin at 135xc2x0 C. is in the range of 0.5 to 6 dl/g and a boiling trichloroethylene-insoluble content is less than 5% by weight, and the propylene polymer is produced by polymerizing propylene alone or copolymerizing propylene and ethylene and/or an alpha-olefin of 4-20 carbons in the presence of a homogeneous catalyst comprising a hafnium compound and an aluminoxane, which is a kind of metallocene compounds.
JPA-9-12635 discloses propylene elastomers containing 50-85 mol % of a propylene unit, 5-40 mol % of a 1-butene unit and 10-40 mol % of an ethylene unit, having the content of the 1-butene unit greater than that of the ethylene unit and having 0.1 to 12 dl/g of an intrinsic viscosity (xcex7) measured in decalin at 135xc2x0 C. and less than 3 of a polydispersity index (Mw/Mn), and a process for the production of the propylene elastomer by copolymerizing propylene, 1-butene and ethylene in the presence of a homogeneous or supported catalyst for olefin polymerization which comprises a metallocene compound represented by the specific formula and at least one compound being capable of activating the metallocene compound and selected from an organoaluminum compound, an organoaluminumoxy compound and a compound forming an ion pair by reacting with the metallocene compound. The propylene elastomers obtained in the examples have the melting point (Tm) lower than the copolymers disclosed in JPA-2-173016.
As disclosed in JPA-2-173016, the melting point (Tm) of the copolymer comprising propylene as a principal component lowers in inverse proportion to the content of a comonomer component. In both publications as recited above, the heat-sealing property of the film and the elastomeric property of the composition are exhibited by utilizing the lowering in melting point due to the use of the specific metallocene compound as a catalyst for the copolymerization of propylene, ethylene and xcex1-olefin and the lowering in melting point due to the presence of a comonomer.
The boiling trichloroethylene-insoluble content disclosed in JPA-2-173016 shows the content of a high crystalline component in the copolymer. The content of a low molecular weight component in the copolymer is determined as the amount of the component eluted in o-dichlorobenzene as mentioned later. The low molecular weight component in the copolymer is a tacky component and gives an influence on the blocking property of the molded product.
In general, the melting point (Tm) of a propylene copolymer is depending on the molecular weight and crystallinity of the copolymer, and the physical properies of the molded products comprising a propylene copolymer as a base resin, especially rigidity and heat resistance are better with higher melting point of the base resin.
An object of the invention is to provide a propylene/ethylene/C4-C20 xcex1-olefin terpolymer which is low in the reduction of molecular weight even in a relatively high comonomer content, less in the amount of component eluted in o-dichlorobenzene at low temperatures which may be a surface tack component of a film, and relatively high in the melting point.
Another object of the invention is to provide a process for the production of the terpolymer using a metallocene catalyst system.
A further object of the invention is to provide a resin composition comprising the terpolymer as a base resin and a molded product formed therefrom.
The present invention is directed to a propylene/ethylene/xcex1-olefin terpolymer characterized in that
i) there is from 0.01 mol % to less than 15 mol % of a comonomer unit with a molar ratio of ethylene units/C4-C20 xcex1-olefin units being in the range of from 6.5xc3x9710xe2x88x924 to 0.99, and from more than 85 mol % to not more than 99.99 mol % of a propylene unit with 2,1- and 1,3-propylene units being in the range of from 0 to 1 mol %, in a polymer chain determined by 13C-NMR spectroscopy;
ii) a weight average molecular weight (Mw) determined by GPC is in the range of from 40,000 to 1,000,000; and
iii) the amount of the component eluted in o-dichlorobenzene at a temperature of not higher than 40xc2x0 C. is not more than 10% by weight based on the total weight of the terpolymer and the amount of the component eluted in o-dichlorobenzene within the xc2x110xc2x0 C. range of an elution peak temperature is not less than 75% by weight, based on the weight of the component eluted at a temperature of higher than 0xc2x0 C.
The present invention is also directed to a process of producing the propylene/ethylene/xcex1-olefin terpolymer, which comprises copolymerizing propylene, ethylene and an xcex1-olefin of 4 to 20 carbons in the presence of a catalyst for an olefin polymerization which comprises a metallocene compound represented by formula (1) 
wherein M represents titanium or zirconium, each X independently represents a hydrogen atom, a halogen atom or a hydrocarbyl radical, (C5H4xe2x88x92mR1m) and (C5H4xe2x88x92nR2n) represent a substituted cyclopentadienyl group in which m and n are an integer of 1 to 3, R1 and R2 each independently represent a hydrocarbyl radical of 1 to 20 carbons, a silicone-containing hydrocarbyl radical or a divalent group in which both of two R1s and two R2s respectively can joint or either of two R1s and two R2s can joint with adjacent two carbon atoms on the cyclopentadienyl ring to form one or more hydrocarbon rings of 4 to 8 carbons which may be substituted by said hydrocarbyl radical, with the substitution position of R1 and R2 on the two cyclopentadienyl rings being arranged so as not to have a symmetry plane containing M, and Q represents a silicon atom or a germanium atom, and each R0 independently represents a hydrogen atom, a halogen atom or a hydrocarbyl radical;
an aluminoxane;
a fine particle support; and
an organoaluminum compound.
The present invention is further directed to a resin composition comprising the terpolymer as a base resin and a molded product formed therefrom.
The present invention is further directed to a propylene multi-layer film having a heat-seal layer formed from the resin composition comprising the terpolymer as a base resin.